For decades there have been discussions about the necessity and optimal length
of dry cow periods. Yet, there is still a lack of information referring to
special questions. The effects of dry period length on metabolism and
productive efficiency are particularly well studied. However, there are hardly
any studies investigating udder health, although udder diseases stand next in
line to reproductive issues and lameness problems, when looking into reasons
for culling. The objective of this study was to investigate the impact of
different dry period lengths on udder health in the subsequent lactation.
Therefore, a four week dry period was compared to a standard eight week dry
period. This study was conducted between April and October 2006 on the
research farm of the Landesanstalt für Landwirtschaft, Forsten und Gartenbau
Sachsen-Anhalt. Data from 75 cows were analyzed in this study. Cows were
enrolled in one of two groups: group L (long) with an eight week dry period (n
= 39 cows) and dry-off at day 56 prior to calving, and group S (short) with a
four week dry period (n = 36 cows) with dry-off at day 30 prior to calving.
Cows in group L were fed a low energy diet from dry-off until day 30 prior to
calving. Then all cows were fed a moderate energy diet. Multiple milk samples
for cyto-bacteriological analysis were taken before dry-off and after calving.
Clinical examinations, i.e. inspection and palpation of the udder, were
performed at dry-off and prior to calving. Farm documentation was included in
the statistical analysis. The results show that cows with a shortened dry
period had higher somatic cell count in milk for at least one week after the
onset of lactation, compared to cows with eight week dry periods. Furthermore,
it was found out for cows of both groups that non-physiological udder forms
are associated with higher somatic cell count in milk before dry-off.
Asymmetric udders are associated with higher somatic cell count in milk 21
days after calving. Short dry periods are detrimental for milk production. In
conclusion, a shortened dry period can have a detrimental impact on milk
production and somatic cell count. Cows with increased somatic cell count in
their previous lactation should still be subjected to an eight week dry period
to assure sufficient udder regeneration. Farms with high somatic cell count
should take this into consideration when determining their dry period length.
It is recommended that one should conduct clinical udder examination and
determination of somatic cell count before selecting the appropriate dry
period length. Based on these findings, it is possible to assume how
subsequent lactation may develop for any cow. Asymmetric udders and high
somatic cell count at dry-off are strong arguments against a shortened dry
period.